The present invention relates to a composition for coating glass fibers that are to be twisted and used in textile products.
Twisted glass fiber strands are produced by attenuating streams of molten glass from orifices in a bushing which contains the molten glass. A winder attenuates the stream of molten glass and as the streams of glass cool to produce filaments they are coated with a sizing composition. Then the filaments are gathered together and wound on a package by the winder. In the production of glass fiber strand for textile applications, a large number of streams of molten glass are attenuated through a large number of orifices on a bushing to produce a glass fiber strand that contains many glass fiber filaments. The fiber size composition provides lubrication and protection of the glass fiber filament and even the glass fiber strand to prevent interfilament abrasion both during the wet conditions occurring during fiber attenuation and under the substantially dry conditions of the conversion of glass fiber strand into products and the further fabrication of these products into other products such as cloth.
Glass fiber strands that are produced for textile applications are drawn over numerous guide surfaces at high rates of speed during the twisting, beaming, quilling and weaving operations to produce the glass fiber textile products. Traditionally the size composition used on glass fibers intended to be used in textile applications has been based on starch and/or oil dissolved in an aqueous medium. Typical size composition contain partially or fully dextrinised starch in amounts of about seven percent by weight and a hydrogenated vegetable oil in an amount of around two percent by weight along with cationic wetting agents, emulsifying agents and water. The art has suggested many improvements of this basic size composition. The oils that have been used have been combinations of cationic lubricants, which are soluble in aqueous starch solutions, and nonionic lubricants which appear to break up the starch film-forming materials and help in reducing tensions that are developed when the bundle of fibers is drawn over guide surfaces. Also small amounts of film-formers such as gelatin and polyvinyl alcohol have been added. Even with all the modifications of the basic starch, or oil and starch lubricant size composition, none of the size compositions have fulfilled all the requirements and conditions necessary to produce a twisted glass fiber strand or strands which can be used directly in the fabrication of textile glass fiber products.
Even the traditional size composition for glass fibers that are to be used in textile applications has a processing disadvantage. The starch which provides adhesion between the glass fibers in the strand is not a permanent film former which can protect the fibers during their ultimate usage. Hence the starch must be burned off of the fibers after they have been processed through the weaving operation. The burning process takes place as a heat cleaning operation where the starch is removed from twisted glass fiber strands. The burning process of most starch usually leaves a minor amount of black, objectionable residue on the glass fiber strand, also causes the loss of some of the tensile strength of the glass fibers, and also necessitates a retreating step. In the retreating step the glass fibers are retreated with a more permanent film former which is usually a silane coupling agent to protect the glass fibers during the further processing to produce textile glass fiber products. The heat cleaning is conducted at a temperature of about 1200.degree. to 1400.degree. F. for 30 to 40 seconds and is sufficient to volatilize the solids and remove them from the fabric and to soften the glass fibers in the woven fibric to set them in their new position. The art has made attempts to replace the starch with a synthetic polymer film former because of the greater uniformity of such materials, but synthetic polymers generally suffer from the problem of producing to high of a tension when the bundles of glass fibers are drawn over the guide surfaces. One recent approach to this dilemma of not being able to use a size composition as a protective coating for the glass fibers through the complete process of forming, twisting, quilling, beaming, and weaving to produce textile glass fiber products, is disclosed in U.S. Pat. No. 4,009,317 (Chase et al) wherein a coating material is provided that has improved burnoff properties. Such an approach, however, does not reduce the need of a heat cleaning operation wherein the size composition is burned from the glass fiber strands.
It is also well known in the art that silanes containing an amino group can be used in treating glass fiber to improve the chopp ability of the fibers by making the fibers more brittle.
In U.S. Pat. No. 3,869,308 (Graham) a sizing agent is disclosed for fiber glass strand or yarn to be used for screening applications where the yarn or strand does not have a detrimental cross-sectional flattening. The sizing agent contains a starch, a salt of a polyamino-functional polyamide resin and a carboxylic acid, a wax, and a fatty triglyceride and can contain a silane coupling agent.
It has recently been suggested in U.S. Pat. No. 3,746,738 (Pepe et al) that polyazamides containing silicon moieties are useful as fiber sizers for fibers such as glass fiber, nylon, polypropylene, polyester and other fibers. The use of the fiber size with glass fibers is exemplified by preparing a 50 weight percent methanolic solution of a modified polyazamide as a 0.5 weight percent solids aqueous solution, which is used to impregnate continuous glass roving. The impregnated roving is then dried and chopped into quarter inch discontinuous strands.
It has also recently been suggested in U.S. Pat. No. 4,055,701 (Marsden) to use azido-containing silane compositions as coupling agents to enhance the adhesion of various substrates with a broad variety of polymers. For example a 5 weight percent aqueous azido-silane product solution using 66 grams of gamma-aminopropyltriethoxysilane and 67 grams of 3-(azido-sulfonylbenzoic acid) is used to coat water--sized fiber glass virgin roving and the treated fiber glass strand is then dried and chopped into one quarter inch long strand.
The object of the present invention is to provide a forming size for use on glass fibers to be used in producing twisted glass fiber yarn that provide the desired protection and tension needed during the operation of forming, twisting, quilling, beaming, and weaving and that reduce the necessity of burning off the size composition from the twisted glass fiber yarn after the yarn is woven.
Another object of the present invention is the provision of a forming size composition for use in producing twisted glass fiber yarn that substantially alleviates the necessity of burning off the non-permanent film forming oil composition of a typical sized formulation and retreating the heat cleaned yarn or fabric with a composition containing a coupling agent.
A further object of the present invention is to provide a forming size composition for use in producing twisted glass fiber yarn that performs the function of film former and coupling agent and that gives flexibility to the glass fibers enabling the glass fibers to be twisted and that need not be removed from the twisted glass fiber yarn since the size composition bonds with the glass and with most chemical polymer and resin compositions.